At this time, there are few clues to what moti­vated Wash­ington Navy Yard gunman Aaron Alexis.

Sources tell the Asso­ci­ated Press that inves­ti­ga­tors have found no man­i­festo or other writ­ings sug­gesting a polit­ical or reli­gious agenda, and the search for answers continues.

Jack Levin, the Brud­nick Pro­fessor of Soci­ology and Crim­i­nology at North­eastern Uni­ver­sity, is the author of “Serial Killers and Sadistic Mur­derers: Up Close and Personal.”

He says Alexis may have had a grudge against the Navy.

I’ve seen that in almost every mass killing, whether it’s a ram­page shooting or a work­place murder or a family anni­hi­la­tion — there’s always the idea of revenge,” Levin says.

Watch the attached video for the com­plete interview.

Read the article at NECN →